Control moment gyroscope arrays, reaction wheel arrays, and other such devices deployed onboard spacecraft for attitude adjustment purposes generate vibratory forces during operation. Spacecraft isolation systems are commonly employed to minimize the transmission of vibratory forces emitted from such attitude adjustment devices, through the spacecraft body, to any vibration-sensitive components (e.g., optical payloads) carried by the spacecraft. Spacecraft isolation systems commonly include a number of individual vibration isolators (typically three to eight isolators), which are positioned between the spacecraft payload and the spacecraft body in a multi-point mounting arrangement.
Spacecraft isolation systems are often also equipped with launch lock assemblies that are positioned between the spacecraft and the payload support structure in parallel with the isolators. During spacecraft launch, the launch lock assemblies maintain the payload support structure in a fixed spatial relationship with the spacecraft. In so doing, the launch lock assemblies shunt significant inertial or shock loads generated during spacecraft launch around the isolators to protect the isolators from damage that might otherwise occur. At a desired juncture after launch, the launch lock assemblies are actuated to allow relative movement between the payload support structure and the spacecraft. For example, in an implementation wherein the spacecraft isolation system includes a number of single DOF, three parameter isolators of the type described above, the isolators may be maintained in a compressed state by the launch lock assemblies prior to launch. The isolators are preloaded in their compressed stage and biased toward design or free length positions. When the launch lock assemblies are actuated as hereinafter described, the isolators expand axially into the design position and displace the payload support structure outward from the spacecraft body. The payload support structure, supported by or “floating on” the isolators, is now able to move relative to the spacecraft and the isolators function collectively to dampen vibrations transmitted between the payload support structure and the spacecraft body.
Each launch lock assembly includes first and second mount pieces that are affixed to the payload support structure and to the spacecraft, respectively. In a bolt-stretch type of launch lock assembly, for example, a specialized bolt normally maintains the first and second mount pieces in clamped engagement. Upon launch lock assembly actuation, an actuator stretches the bolt to increase its axial length without snapping or fracturing the bolt, releasing the first and second mount pieces from clamped engagement, thereby creating an axial gap therebetween and enabling the isolators to expand axially into the design position as noted above. Launch lock assemblies, including such bolt-stretch launch lock assemblies and other types of releasable clamping mechanisms, may include at least one axial gap amplification device as described in co-pending application Ser. No. 13/406,647 entitled “Launch Lock Assemblies including Axial Gap Amplification Devices and Spacecraft Isolation Systems Including the Same” filed Feb. 28, 2012 by Honeywell International Inc., the assignee of the instant application, to increase the length of the axial gap created between the first and second mount pieces beyond that directly attributable to stretching of the bolt or other axially-stretchable member. It is generally desirable to maximize the axial length of gaps to provide isolators with a sufficient range of motion to optimize the damping performance of the multi-point isolation system. The axial gap created is on one side of the first mount piece only (i.e., a one-sided gap). Preload, provided by the isolators, moves the first mount piece into the center of the one-sided gap, providing necessary axial clearance on both sides of the first mount piece. Effecting movement of the first mount piece into the one-sided gap upon launch lock assembly actuation makes preload requirements higher. Therefore, the increase in length of the axial gap provided by the axial gap amplification device is limited by the preload that can be applied thereto.
Accordingly, it is desirable to provide a launch lock assembly with reduced preload and a spacecraft isolation system including the same. It is also desired to provide a launch lock assembly with reduced preload to increase the length of the axial gap created between the first and second mount pieces beyond that directly attributable to stretching of the bolt or other axially-stretchable member, without the increase in length being limited by preload forces. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the present invention and the appended claims, taken in conjunction with the accompanying drawings and this Background of the invention.